1. Field of Technology
The present invention relates to or reproduction methods, data processing apparatuses and programs.
2. Description of Related Art
Color printing apparatuses that reproduce color by the combination of an achromatic color material and a plurality of chromatic color materials and by their density adjustment have been known. As an example, one can give a CMYK method color printing apparatus that reproduces colors by superimposing chromatic toners of the colors cyan (C), magenta (M), yellow (Y) and a black (K) achromatic toner. In the following, explanations are given taking the example of a CMYK method color printing apparatus, and black (K) which is an achromatic toner is referred to as a black plate.
A color printing apparatus forms images on a printing medium (for example, paper, etc.) in accordance with the image data whose printing has been requested. At that time, if the image data is the same and the color printing apparatuses forming the image are different, very often the color reproduction of the image formed on the printing medium is different. In other words, in general, the color reproduction characteristic of printing vary depending on the individual color printing apparatus. Because of this, as a rule, in order to verify the color reproduction of a certain color printing apparatus, it is necessary to print using that color printing apparatus, and to verify that printed material.
On the other hand, there is a demand for carrying out printing using a small scale color printing apparatus before carrying out printing using a large scale of printing apparatus, to verify in advance the color reproduction at the time of printing. In view of this, there is a method of, based on the color control values corresponding to the color reproduction by a certain color printing apparatus (hereinafter referred to as a first color printing apparatus), calculating the color control values of a different color printing apparatus (hereinafter referred to as a second color printing apparatus) and simulating the color reproduction by a first printing apparatus using a second color printing apparatus (ink simulation). In other words, by calculating second color control values based on first color control values at the time of printing image data, and by printing that image data using a second color printing apparatus based on the calculated color control values, it is possible to simulate the color reproduction when that image data is printed using a first color printing apparatus.
As a concrete method of ink simulation there is profile color conversion of, based on the color profile of a first color printing apparatus and the color profile of a second color printing apparatus, converting first color control values into second color control values. In profile color conversion, a color profile (ICC file) is used whose specifications have been standardized by the International Color Consortium, (hereinafter referred to as ICC). The ICC profile has the color control values of a plurality of devices including various types of color printing apparatuses, and information indicating the correlative relationship with the profile connection space (hereinafter referred to as PCS) which has color values (CIE XYZ or CIE L*a*b*) in a three dimensional color space that does not depend on the different devices. Profile color conversion converts first color control values into color values in the PCS, and second color control values are calculated based on the color values after conversion.
However, as is shown in FIG. 12, in the color reproduction by a color printing apparatus of the CMYK method, when a black plate (K) is added to the color (hereinafter referred to as a first color) that is reproduced by the combination of the colors cyan (C), magenta (M), and yellow (Y), a second color is obtained that has lower brightness and color saturation than the first color The ratio of brightness and color saturation of the second color with respect to the first color is determined by the density of the black plate.
The density mentioned here indicates the quantity of toner per unit area, is controlled in the range from 0 to 100(%), and this quantity is determined by the color control values. The control of density by color control values is not limited to black plates but can be applied to the quantity of each toner and the color control values of color reproduction are expressed as CMYK=(a%, b%, c%, d%). Here, values in the range from 0 to 100 are used for each of the symbols a, b, c, and d, and indicate the quantity of each toner at the time of color reproduction of different colors. The increase or decrease of the brightness and color saturation due to the density of the black plate corresponds to the value of d.
The color reproduction of the second color by the superimposition of a black plate on a first color, apart from obtaining enhanced quality perception of color reproduction due to the addition of late, also causes visual effects such giving contrast variation to the printed image, etc. Therefore, expecting such visual effects, color reproduction of the second color is likely to be carried out by intentional use of a black plate. Therefore, in ink simulation, so that the effects due to the addition black plate during printing in the first color printing apparatus are not lost even during printing in the second color printing apparatus, addition of a black plate (black plate maintenance) is demanded at the time of printing in the second color printing apparatus.
On the other hand, as is shown in FIG. 13, the brightness reduction pattern due to a black plate may differ depending on the printing apparatus. In a similar manner, even the color saturation reduction pattern due to a black plate may also differ depending on the printing apparatus. Because of this, at the time of carrying out ink simulation, the black plate density may change, and as a result it may not be possible to carry out black plate maintenance. For example, when the second color control values are calculated by profile color conversion based on the color control values CMYK=(0%, 50%, 50%, 12%) including a black plate in a first color printing apparatus, there are situations when values will become CMYK=(5%, 56%, 56%, 0%) and the black plate Is lost, This is due to various reasons such differences In the color characteristic of the toners among the different color printing apparatuses, or when an achromatic color, that is black, is reproduced using color printing apparatus of the CMYK method, apart from the case reproducing black color using on black (K) color toner, can be reproduced using mixed colors by combining cyan (C), magenta (M), and yellow (Y).
In view of this, as a method of black plate maintenance, a method has been known of first determining the black plate density to be used in the second color printing apparatus, that is, in the printing apparatus on the output side, and of determining the appropriate CMY plate color control values based on that black plate density and the reproduction target color values in a three dimensional color space that is independent of the device (for example, see Japanese Unexamined Patent Application Publication No. H9-186894, and Japanese Unexamined Patent Application Publication No. 2007-43250).
However, there are cases in which it is not possible to use the black plate maintenance method described in Japanese Unexamined Patent Application Publication No. Hei 9-186894 and Japanese Unexamined Patent Application Publication No. 2007-43250 (hereinafter referred to as the conventional plate maintenance method).
When using the conventional black plate maintenance method, data will be necessary that gives the correlative relationship between the combination of the PCS color values for determining the color control values for a CMYK method color printing apparatus based on the PCS color values and the black plate control values for the second color printing apparatus and the black plate control values and the CMYK plate color control values. Since this correlative relationship is dependent on a specific ICC profile, even the data indicating this correlative relationship for each ICC profile will be different from each other.
Because of this, when using the conventional black plate maintenance method, it is necessary to restrict the ICC profiles used in the second color printing apparatus in order to prepare the data indicating the correlative relationship between the combination of PCS color values and black plate control value and the CMYK plate color control values.
On the other hand, in recent years, there are printing apparatuses in which the user can freely change the ICC profile such as the multifunction PostScript Printers, etc. In the case of a printing apparatus in which the ICC profile changed, if an ICC profile is used for the data indicating the correlative relationship between the combination of PCS color values and black plate control value and the CMYK color control values, is not possible to use the conventional black plate maintenance function.
The problem to be solved by the present invention is to provide a black plate maintenance function with far higher general purpose applicability.